Illinois Water Quality Report: 11,489 Water-System Violations Mapped to 923 ZIPs
2,216 water systems · 923 ZIP codes · 11,489 violations
Data: EPA Safe Drinking Water Information System (SDWIS), EPA ECHO
ZipCheckup tracks EPA drinking-water compliance for 2,216 public water systems serving 923 ZIP codes in Illinois. The state record shows 11,489 EPA violations, 587 health-based.
City Water Quality Map: Illinois
Each circle represents a city. Size indicates population, color indicates water quality grade. Tap a circle for details.
Cities with Most Violations in Illinois
| # | City | Grade | Violations | Systems | Population | |
|---|---|---|---|---|---|---|
| 1 | Joliet | 161 | 13 | 130,147 | Details → | |
| 2 | Mchenry | 158 | 8 | 55,801 | Details → | |
| 3 | Chicago Heights | 144 | 5 | 52,395 | Details → | |
| 4 | Springfield | 116 | 15 | 137,953 | Details → | |
| 5 | Fox Lake | 114 | 5 | 10,846 | Details → | |
| 6 | Litchfield | 91 | 5 | 8,591 | Details → | |
| 7 | Ringwood | 90 | 5 | 888 | Details → | |
| 8 | East Moline | 84 | 5 | 23,288 | Details → | |
| 9 | Round Lake | 83 | 5 | 62,000 | Details → | |
| 10 | Lockport | 81 | 5 | 36,841 | Details → |
Most Common Contaminants in Illinois
| Contaminant | Category | Violations | ZIPs Affected | Health Risk |
|---|---|---|---|---|
| Consumer Confidence Rule | Reporting | 1,582 | 604 | No |
| Public Notice Rule | Reporting | 1,121 | 369 | No |
| Lead and Copper Rule | Treatment Technique | 976 | 444 | Yes |
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 942 | 461 | Yes |
| Haloacetic Acids (HAA5) | Disinfection Byproducts | 812 | 390 | Yes |
| Lead and Copper Rule Revisions | Treatment Technique | 621 | 345 | Yes |
| Turbidity | Treatment Technique | 492 | 82 | No |
| E. coli | Microbiological | 492 | 82 | No |
| Cryptosporidium | Microbiological | 492 | 82 | No |
| Total organic carbon | Disinfection Byproducts | 415 | 112 | Yes |
Water Quality Overview
Illinois has 2,216 community water systems represented across 923 directly mapped ZIP records. The associated city records cover approximately 12,349,693 people. The available records contain 11,489 EPA violations, including 587 health-based violations.
Health-based violations account for 5% of all violations in Illinois. These violations indicate contaminant levels that may pose direct risks to human health, as opposed to monitoring or reporting failures.
Violation Breakdown
| Violation Type | Count | Percentage |
|---|---|---|
| Health-based | 587 | 5.1% |
| Monitoring/Reporting | 10,902 | 94.9% |
| Total | 11,489 | 100% |
Health-based violations are MCL, MRDL (disinfectant) and treatment-technique violations. Monitoring violations indicate failures to test or report - these do not necessarily mean unsafe water, but they mean the water was not properly verified.
Cities with Most Violations
The following cities in Illinois have the highest number of EPA violations:
| Rank | City | Violations | Water Systems | Population |
|---|---|---|---|---|
| 1 | Joliet | 161 | 13 | 130,147 |
| 2 | Mchenry | 158 | 8 | 55,801 |
| 3 | Chicago Heights | 144 | 5 | 52,395 |
| 4 | Springfield | 116 | 15 | 137,953 |
| 5 | Fox Lake | 114 | 5 | 10,846 |
| 6 | Litchfield | 91 | 5 | 8,591 |
| 7 | Ringwood | 90 | 5 | 888 |
| 8 | East Moline | 84 | 5 | 23,288 |
| 9 | Round Lake | 83 | 5 | 62,000 |
| 10 | Lockport | 81 | 5 | 36,841 |
Violation counts are cumulative across all water systems serving each city. Higher counts may reflect larger systems with more monitoring requirements, not necessarily worse water quality.
Violation Trend Over Time
Year-by-year EPA violations recorded across all water systems in Illinois:
| Year | Health-based violations |
|---|---|
| 2021 | 57 |
| 2022 | 50 |
| 2023 | 47 |
| 2024 | 285 |
| 2025 | 98 |
| 2026 | 19 |
Health-based violations have decreased from 57 in 2021 to 19 in 2026, suggesting improving compliance across Illinois.
Most Common Contaminants
The following contaminants have caused the most violations across Illinois water systems:
| Contaminant | Category | Violations | ZIPs Affected | Health-Based |
|---|---|---|---|---|
| Consumer Confidence Rule | Reporting | 1,582 | 604 | No |
| Public Notice Rule | Reporting | 1,121 | 369 | No |
| Lead and Copper Rule | Treatment Technique | 976 | 444 | Yes |
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 942 | 461 | Yes |
| Haloacetic Acids (HAA5) | Disinfection Byproducts | 812 | 390 | Yes |
| Lead and Copper Rule Revisions | Treatment Technique | 621 | 345 | Yes |
| Turbidity | Treatment Technique | 492 | 82 | No |
| E. coli | Microbiological | 492 | 82 | No |
| Total organic carbon | Disinfection Byproducts | 415 | 112 | Yes |
| Combined Radium (-226 and -228) | Radionuclides | 322 | 111 | Yes |
How to Check Your Water in Illinois
Enter your ZIP code on ZipCheckup for detailed water-system data including contaminant levels and violation history; the separate Home Safety Score is a multi-source index
Request your CCR - every water utility must provide an annual Consumer Confidence Report
Get a home test - certified kits ($20-$50) or professional lab tests ($150-$400)
Consider filtration - NSF-certified filters can address specific contaminants found in your area
EPA Enforcement
The EPA and state regulators have taken enforcement actions against water systems in Illinois. Enforcement actions range from compliance assistance to formal orders and penalties.
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Enforcement: EPA ECHO
Updated daily.
What are EPA violations?
Health-based violations are EPA violations of a Maximum Contaminant Level (MCL), a Maximum Residual Disinfectant Level (MRDL) or a required treatment technique - the enforceable standards designed to protect human health. Illinois has 587 such violations across its water systems. Not all violations cause illness; review each violation type and duration to understand possible health implications.
Understanding water quality grades
ZipCheckup grades water systems from A to F based on EPA violation history, contaminant levels, and system compliance. Grades summarize ZipCheckup's scoring inputs; review the underlying records for specific issues. Grades are calculated per ZIP code and aggregated at the city, county, and state level.
Wondering about your tap water?
Water quality varies by ZIP code. Enter yours to see contaminant data, violations, and filtration recommendations specific to your area.
Check Your ZIP Code Water Quality →Frequently Asked Questions
Is the tap water safe to drink in Illinois?
Records for 2,216 community water systems mapped to ZIPs in Illinois show 11,489 reported violations, including 587 health-based. Water quality varies by city and ZIP code - check your specific location for detailed results.
How many violations are on record for water systems serving Illinois?
Illinois has 11,489 EPA violations on record across 923 ZIP codes; 587 are classified as health-based violations. The remainder are monitoring or reporting violations.
Which city in Illinois has the worst water quality?
Joliet, IL has the most recorded EPA violations (161) among the cities with mapped water systems in Illinois in our data. Check your water supplier's report and test your tap water for the most accurate picture of your local water quality.
Which city in Illinois has the best water quality?
Violation records vary by water system across Illinois. Check individual city reports for details.
What contaminants are found in Illinois drinking water?
EPA regulates over 90 drinking-water contaminants nationally; water systems in Illinois monitor those applicable to each system, which can include lead, copper, nitrate, disinfection byproducts, and bacteria. The most common violations vary by region - check your ZIP code for contaminant-specific data.